Flame retardant composition containing tetrakis (hydroxymethyl) phosphonium oxalate

ABSTRACT

Durable flame retardancy and a soft hand are imparted to cellulosic textile materials by applying and curing an aqueous solution of tetrakis(hydroxymethyl)phosphonium oxalate and urea, a melamine, or a methylolated nitrogenous cellulose reactant or mixtures thereof to the textile materials.

United States Patent Chao June 10, 1975 [54] FLAME RETARDANT COMPOSITION 3,698,854 10/1972 Donaldson et a1. 8/ 1 16 P CONTAINING TETRAKIS 3,799,738 3/1974 Wagner 8/116 P X (HYDROXYMETHYL) PHOSPHONIUM DXALATE inventor: Tsai Hsiang Chao, Somerville, N].

American Cyanamid Company, Stamford, Conn.

Filed: Dec. 26, 1972 Appl. No; 317,998

,Assignee:

US. Cl. 252/81; 8/116 P; 117/136 Int. Cl. B27k 3/00 Field of Search 252/81; 8/116 P; 117/136 References Cited UNITED STATES PATENTS l3 9/197l Stock et a]. 8/116 P X Primary Examiner-Stephen .1. Lechert, Jr. Attorney, Agent, or Firm-H. G. Jackson thyl)phosphonium oxalate and urea, 21 melamine, or a methylolated nitrogenous cellulose reactant or mixtures thereof to the. textile materials.

4 Claims, No Drawings FLAME RETARDANT COMPOSITION CONTAINING TETRAKIS (HYDROXYMETHYL) lPI-IOSPIIONIUM OXALATE BACKGROUND OF THE INVENTION 1. Field of the Invention The invention pertains to chemical flame retardants for textiles.

2. Description of the Prior Art Phosphonium salts of the formula (HOCH P C- H OH.X wherein X is an anion are used in flame retardant finishes. Tetrakis(hydroxymethyl)phosphonium chloride (THPC) is a component of some flame retardant finishes for textile materials. When tris(hydroxymethyl)phosphine (THP) is applied to cellulosic materials with organic nitrogenous compounds which contain trivalent nitrogen atoms having at least two hydrogen atoms or methylol groups, the treated textile materials have flame retardant properties which are durable to repeated laundering but the finishes impart a stiff, boardy hand and cause an objectionable and sometimes severe strength loss in the treated fabric. Textile tensile strength, tear strength and abrasion resistance are reduced.

US. Pat. Nos. 2,892,803 and 3,236,676 teach the use of tetrakis(hydroxymethyl)phosphonium phosphate (TKPP) and tetrakis(hydroxymethyl)phosphonium acetate (TKPA) as flame retardants in finishes containing nitrogenous compounds. Finishes containing TKPP impart good flame retardance which is durable to laundering, but the treated fabrics are stiff and boardy and suffer from undesirable strength loss. Finishes containing TKPA also impart good flame retardancy, but the acetate is considerably less stable than the corresponding chloride and phosphate salts, resulting in application problems such as inefficient fixation on the textile material and offensive odors.

My invention provides a flame retardant finish for cellulosic textile materials which imparts a soft hand to the material, i.e., it does not make the material stiff; the materials treated with the finish are durable to repeated laundering; and the finish does not reduce the resistance of fabric to wear.

U.S. Pat. No. 2,937,207 teaches a process for manufacturing tetrakis(hydroxymethyl)phosphonium oxalate. The patent suggests that the products obtained according to the process of the invention can be used as flame-proofing agents for textiles and woods. However, as shown by my Example 4, below, when tetrakis(hydroxymethyl)phosphonium oxalate is used alone on fabric, the fabric burns even before laundering.

SUMMARY OF THE INVENTION The invention is a process for imparting durable flame retardant properties and a soft hand to cellulosic textile materials by applying an aqueous finish solution of tetrakis(hydroxymethyl)phosphonium oxalate and at least 1 organic nitrogenous compound having a trivalent nitrogen bearing at least 2 members comprised of hydrogen atoms and methylol groups, for example, urea, a melamine or a water soluble methylolated nitrogenous celluose reactant or mixtures thereof to the textile material and heating the textile material to effect a cure of the finish thereon; the finish compositions and the cel-lulosic textile material produced by my pro- DETAILED DESCRIPTION I have discovered that when an aqueous solution containing tetrakis(hydroxymethyl)phosphonium oxalate (TKS) and a nitrogenous compound having trivalent nitrogen bearing at least 2 hydrogen atoms or methylol groups is applied to cellulosic textile materials, the materials become flame retardant without appreciable change in hand or severe strength loss and the flame retardancy is durable to repeated launderings. These improvements are particularly surprising in view of the comments, above, regarding TKPP and TKPA when applied separately or even in blends.

The aqueous solutions of tetrakis(hydroxymethyl)- phosphonium oxalate (TKS) can be prepared by reacting in aqueous medium 1 mol of tris(hydroxymethyl)- phosphine with at least 1 mole of formaldehyde and essentially one-half mole of oxalic acid. Sufficient oxalic acid is used to provide between 0.3 and 1.0 moles, preferably between 0.4 and 0.6 moles, of real oxalic acid per mole of THP. The formaldehyde should be used in an amount sufficient to provide one mole of formaldehyde per mole of THP. The formaldehyde can be in the form of an aqueous solution or as paraformaldehyde. When the initial exothermic reaction subsides, the temperature of the mixture is held at about 30C. for about 4 hours. The reaction temperature should be between 20C. and C., preferably between 25C. and 50C.

The product is an aqueous solution which can be used in preparing the flame retardant finishes. The finish may contain free formaldehyde and oxalic acid. The amount of TKS'present in the product depends on the amount of TH? used initially. Each mole of the THP requiries by theory 0.5 moles ,of oxalic acid and one mole of formaldehyde. For each mole of TKS formed, the amount of THF in the product is reduced by two moles.

The application-solutions are prepared by diluting the aqueous solution of TKS in water to a given concentration of solids and adding urea or a urea formaldehyde condensate in sufficient amount to provide about 1.25 moles prescribed above of urea and/or ureaformaldehyde condensate per mole of phosphonium salts. The concentration phosphorus and urea in the application solutions will depend, in general, on the method of application, the amount of phosphorus and urea to be applied to the textile material, and on the weight, structure and fiber composition of the textile material.

The nitrogenous compounds of use in this invention include the organic amido compounds which are conventionally employed in the form of their methylol derivatives as thermosetting aminoplast textile finishes. They include the melamines, urea, cyclic ureas, carbamates, triazinones, etc., and their methylol and alkylated methylol derivatives. The preferred nitrogenous compound is urea. Representative methylol compounds include monomethylol urea, dimethylol urea, tetramethylol urea, dimethylol melamine, partially methylated trimethylol melamine, and the like. Combinations of'two or more nitrogenous compounds may be employed.

Sufficient flame retardant finish should be applied to cellulosic textile-material to provide between about 1% and 6%, preferably between about 2% and 4% of phosphorus based on the weight of the textilematerial. Sufficient nitrogenous compound is used to provide between about 1% and preferablybetween about 2% and 6% of nitrogen based on the weight of the textile material.

From these percentages, it is a simple matter to cal- -culate the amounts ofphosphorus-containing compound and nitrogenous compounds to be used in pre paring the flame retardant finishes. The ratio of nitro derived phosphorus on a parts by weight basis is between 0.5 and 5.0 preferably between 0.7 and 2.0.

I I The cellulose textile materialishould contain at least 20% cellulosic fibers. By cellulosic fibers it is meant such fibers as cotton, regenerated cellulose (rayon), linen, jute, etc. Blends of cellulosic fibers or blends of cellulosic fibers with noncellulosic fibers, both natural gen of the nitrogenous compounds to-phosphine- TABLE I On Weight of Bath Pad Bath pH TKS TKP Urea %Powf Hand A 28.0 I I 7.2 3.00 Soft B 5.15 30.4 7.8 3.25 Soft C 5.00 31.8 7.2 3.00 Stiffer D. 5.00 34.4 7.8 3.25 Stilfest owt'= on the weight of the fabric All of the fabrics possessed acceptable flame retarduncy, durable through at Least '70 Kenmore washings, by theDept. of Commerce Test PFF-37() using a 3-sccond and synthetic, such as silk, wool, nylon, polyester,

acrylic, etc., may be used.

The components of the flame retardant compositions temperaturebetween about i67-350F. or higher. The

- drying time'can range from several minutes at the lower temperature to asbriefly as seconds atthe higher tem- I perature. .The finish is then cured at a temperature of between about248--392F. preferably between about 300-350F. The time required for curing the finish is between I and'5 minutes, depending on the tempera ture and the weight and structure of the textilemate rial.

of this invention are applied tothe textile materialfrorn Y the same bath or from separate baths by padding, dip

ping, spraying, etc. The materials are then dried ata The compositions and. processes of the present invention are further described and compared with related compositions and process by the following examples. These examplesare not tobe taken'as being limitative of the present invention. In each case, percentages are by weight unless otherwise indicated.

EXAMPLE 1 EXAMPLE 2 Four pad baths were prepared. Pad Baths A and B contained the product of Example 1, and pad baths C and D contained a 60/40 molar mixture of tetrakis(hydroxymethyl )phosphonium acetate/tetrakis(hydroxy- I treatment.

flame.

EXAMPLE 3 Six pad bathswere prepared. Pad Baths A, Cand E contained TKS (10.2% phosphorus derived from phosphine), and pad baths B, D and F contained T KP (9.8%

phosphorus derived from phosphine); each pad bath also contained urea and 0.56% by weight of a surfactant. The padbaths were applied to cotton flannelette and the treated fabrics were dried-at 225F. for 3.0miriutesand then heated at 350F. for 3.0 minutes. After curing all fabrics were washed in a solution con-- taining 5% real hydrogen peroxide based on the dry weight of the treated fabric using sufficient sodium silicate to maintain apI-I in the range of-9.0 to 9.5 duringthe washing cycle. The compositions of the pad baths and treated fabrics are shown in Table II.

TABLE II On Weight Of Pad Bath Onweight of Fabric Pad Bath TKS TKP Urea P Urea A 30.9 7.65 2.94 7.14 g B 32.3 7.65 3.04 7.37 C 33.5 8.28 3.24 7.86 D 34.9 8.28 3.36 8.10 E 36.1 8.93 3.58 8.66 F 37.6 8.93 3.68 8.93

At all levels of add-on, the TKS-treated fabrics had a softer hand then those treated with TKP. In fact, the hand of the TKS-treated fabric at the 3.58% phosphorus level (pad bath E) was as soft as the TKP-treated fabric at the 3.04% phosphorus level (pad bath B).

The durability of the TKS treatment is about the same as that of the TKP treatment at any level of addon under the same washing conditions.

EXAMPLE 4 A pad bath was prepared containing the product of Example 1 at 32.5% TKS on the weight of the pad bath, the pad bath had a pH of 4.2. The pad bath was applied to 5.5oz/-yd bleached, mercerized cotton at 100% expression, and the treated fabric was dried 4 minutes at 225F. and heated 4 minutes at 325F. to obtain a phos phorus content of 3.5% onthe weight of the fabric. The treated fabric, before process washing, burned completely when subjected to the Dept. of Commerce Test PFF-3-7O using a 3 second flame.

I claim:

ll. An aqueous flame retardant finish composition solution for cellulosic textile materials comprising:

tetrakis(hydroxymethyl) phosphonium oxalate and at least one organic nitrogenous compound having a trivalent nitrogen bearing at least 2 members comprised of hydrogen atoms and methylol groups,

6 phosphorus on a parts by weight basis is between 0.7 and 2.0.

4. A finish composition according to claim 2 comprising 0.3 to 1.0 mole of tetrakis(hydroxymethyl)- phosphonium oxalate and from 0.5 to 2 moles of urea per liter of solution. 

1. AN AQUEOUS FLAME RETARDANT FINISH COMPOSITION SOLUTION FOR CELLULOSE TEXTILE MATERIALS COMPRISING: TETRAKIS(HYDROXYMETHYL) PHOSPHONIUM OXALATE AND AT LEAST ONE ORGANIC NITROGENOUS COMPOUND HAVING A TRIVALENT NITROGEN BEARING AT LAST 2 MEMBERS COMPRISED OF HYDROGEN ATOMS AND METHYLOL GROUPS, OR MIXTURES THEREOF WHEREIN THE RATIO OF NITROGEN OF THE NITROGENOUS COMPOUNDS TO PHOSPHINE-DERIVED PHOSPHOROUS ON A PARTS BY WEIGHT BASIS IS BETWEEN 0.5 AND 5.0.
 2. A finish composition according to claim 1 of tetrakis(hydroxymethyl)phosphonium oxalate and urea.
 3. A finish composition according to claim 2 wherein the ratio of the nitrogen of urea to phosphine-derived phosphorus on a parts by weight basis is between 0.7 and 2.0.
 4. A finish composition according to claim 2 comprising 0.3 to 1.0 mole of tetrakis(hydroxymethyl)phosphonium oxalate and from 0.5 to 2 moles of urea per liter of solution. 